Moving arm up and down (5)

I believe the answer is:

rotor

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This clue could be a double definition.

'moving arm' is the first definition.
'rotor' can be an answer for 'arm' (I have seen 'Revolving arm' mean 'rotor' so perhaps 'arm' could also mean 'rotor'). I'm not certain of the 'moving' bit.

'up and down' is the second definition.

Can you help me to learn more?

(Other definitions for rotor that I've seen before include "Helicopter vane" , "Revolving part of a machine, a palindrome" , "Turning component" , "Revolving dynamic part" , "part of chopper" .)

I've seen this clue in The Globe and Mail.

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